Brakes locking up

[craiggroves91]

Hey guys,

I'm in the stage of working out the little demons after my s52 swap and this brake issue is my biggest problem.

First I'd like to say before I did the swap the brakes functioned fine, if that makes a difference.

My setup is all stock e30 brake parts. I relocated the brake booster and modified the clevis to account for the relocation, it's basically the stock setup moved over.
So here is the issue.

My front brakes (seems to be front brakes only) lock up and don't release until I crack the bleed screw.
I also noticed when I pull the pedal back up the brakes free up quite a bit.
So something its stopping the pressure from being relieved on the front brakes.
The pedal is also very squishy until it gets to one point and then the brakes engage quite harshly. When the car is off the pedal is very stiff.
I have rebuilt the calipers and they seem to be functioning fine.

Any ideas?

Is there a standard distance setting for the pedal? I feel my adjustment for the pushrod might be off

[AndrewBird]

Check the clevis that attaches to the brake pedal. If it is adjusted too long, it will slightly apply the brakes, eventually locking them on. There should be just a bit of play in the brake pedal.

[craiggroves91]

Check the clevis that attaches to the brake pedal. If it is adjusted too long, it will slightly apply the brakes, eventually locking them on. There should be just a bit of play in the brake pedal.

Yeah, thats where I think some of the issue is. I can't find the sweet spot. Any tips for this?

I just found in the bentley a measurement for the pedal to the firewall, so Ill try that out.

[craiggroves91]

Here is my linkage



One thing I noticed is the very far left prong on the clevis is quite close to the pedal and maybe even touching, not sure how much. could this be interfering?

[jlevie]

How much free play is there in the pedal? Does the pedal come all the way up to the stop on it's own?

[craiggroves91]

How much free play is there in the pedal? Does the pedal come all the way up to the stop on it's own?

It comes up on its own fine, I just don't know if it stops where its supposed to stop

[jlevie]

Well, if you pull on the pedal does it move higher?

[craiggroves91]

Well, if you pull on the pedal does it move higher?

Well at one point I was able to pull up and the brakes would free up.
I forgot where its at now because I messed with it so much out of frustration. When it clears up I'm going to adjust the pedal more.

[jlevie]

Well at one point I was able to pull up and the brakes would free up.

That may suggest that something in the pedal or link rod is binding.

[craiggroves91]

That may suggest that something in the pedal or link rod is binding.

It doesn't seem to be binding. The pedal moves freely

[AndrewBird]

If it isn't returning fully on it's own, then it is binding. You might be able to pull it back easily, but that doesn't mean it it can return on it's own.

You don't need a measurement to determine free-play. The rod coming from the booster will sit where it should sit. You need to adjust the clevis until you can move the pedal back and forth slightly without moving the clevis/rod.

[craiggroves91]

If it isn't returning fully on it's own, then it is binding. You might be able to pull it back easily, but that doesn't mean it it can return on it's own.

You don't need a measurement to determine free-play. The rod coming from the booster will sit where it should sit. You need to adjust the clevis until you can move the pedal back and forth slightly without moving the clevis/rod.

Okay thats what I'll try to do. I realized in my other e30 it can wiggle back and forth easily. I'll try to imitate that.

[craiggroves91]

I think the issue is something else. I have tried everything with the pedal. there is play but they are still locked.

[jlevie]

Well, you could have a bad booster...

[craiggroves91]

Well, you could have a bad booster...

Does the booster effect the hydraulics?
I thought all it does is aid in braking.